On 27 September 2012, he made his debut for the first team in the "Eternal derby" win over Hajduk Split (3–1), when he replaced Sammir for the final ten minutes of the match.

This made him the youngest goalscorer in the history of the league, at the age of 16 years and 112 days – breaking the record set in November 2010 by his teammate, Mateo Kovačić.

[9] In November 2012, Halilović scored his second league goal for Dinamo in a 5–0 win against NK Zadar, from outside of the box on an assist provided by Kovačić.

On 24 October 2012, he made his European debut in the 90th minute of the encounter against the French team Paris Saint-Germain at Maksimir Stadium, coming on as a substitute for Kovačić.

He signed a five-year contract for an initial amount of €2.2 million, set to increase if he secures a spot on the first team, and was assigned to the reserves in Segunda División.

[13] Halilović made his first appearance for Barcelona's senior team on 15 January 2015, replacing Adama Traoré for the last 28 minutes of a 4–0 away win against Elche CF in the last 16 of the Copa del Rey.

[16] On 29 August, Halilović made his La Liga debut, coming on as a second-half substitute for Carlos Carmona in a 0–0 away draw against Real Sociedad.

[19] Halilović was a half-time substitute for Nacho Cases on 15 December in the national cup last-32 second leg and scored twice – one a penalty kick – to ensure a 3–3 home draw against Real Betis, who advanced 5–3 on aggregate.

[26] In the first game of the 2017–18 season for Las Palmas, playing against Valencia, Halilović received a straight red card for a tackle on José Gayà, in the 33rd minute.

[32] On 23 November 2020, Halilović joined EFL Championship club Birmingham City as a free agent; he signed until the end of the season.

[35] He scored his first and only goal for Birmingham on 27 February 2021 with "a superb left-footed curler from 20 yards (18 m)" to complete a 2–1 win over Queens Park Rangers.

After a heavy 4–1 loss to Romania,[54] he was left on the bench for the remaining matches against France and England, as Croatia failed to qualify for the knockout stage.